Apparatus for use in the extractorporeal circulation of blood



J1me 1961 A. c. D'ARCEY ETAL 2,988,001

APPARATUS FOR USE IN THE EXTRACORPOREAL CIRCULATION OF BLOOD Filed April30, 1956 4 Sheets-Sheet 1 Pulmonary Artery June 13, 1961 A. c. 'DARCEYETAL 2,988,001

APPARATUS FOR USE IN THE EXTRACORPOREAL CIRCULATION OF BLOOD Filed April30, 1956 4 Sheets-Sheet 2 [nven 101:;

W Alfred C DZI/"cey r Eliot M Wadsworth W By t/zezr Attorney l-lll zJune 13, 1961 A. c. 'DARCEY ETAL 2,983,001

APPARATUS FOR USE IN THE EXTRACORPOREAL CIRCULATION OF BLOOD Filed April30, 1956 4 Sheets-Sheet 3 Fig. 3

Inventars Alfred C Di l/"c619 Eliot M Wadsu/arzh B3 #261)" Azzorney June13, 1961 A. c. DARCE'Y ETAL 2,988,001

APPARATUS FOR USE IN THE EXTRACORPOREAL CIRCULATION OF BLOOD Filed April30, 1956 4 Sheets-Sheet 4 in van tom" Alfred C Dl lrcey Eliot MWadsworth By their Attorney United States Patent 2,988,001 APPARATUS.FOR USE IN THE EXTRACOR- POREAL CIRCULATION OF BLOOD Alfred C. DArcey,Danvers, and Eliot M. Wadsworth,

Beverly Farms, Mass., assignors to United Shoe .Machinery Corporation,Flemington, N..l., a corporation of New Jersey Filed Apr. 30, 1956, Ser.No.'581,730 8 Claims. (Cl. 103-4) This invention rel-ates to apparatusfor .use in the extracorporeal circulation of blood andis hereinillustrated as erribodied in a novel and improved pump of thecompressible tube-rotary impeller type.

As will be appreciated by those skilled in the art, it has been hithertoproposed to provide pumping means located exteriorly of the body fortaking over, respectively, the pumping actions of the right and leftsides of the heart, thus making it possible entirely to bypass the heartduring surgical repair thereof which is very greatly facilitated by thedry field obtained as a result of relieving the heart of its usualtaskof circulating the blood of the patient. Obviously, a primerequisite of a pump of this type is complete dependability, while otherimportant characteristics include simplicity of construction, and easeof operation andcontrol. Inaddition, it is most imperative that thearrangement be such that the introduction of air into the blood streamis effectively avoided and the danger of damage to the bloodcorpuscles,trauma or hemolysis, substantially eliminated. It is,therefore, a principal object of this invention to provide a novel-andimproved pump for use in the extracorporeal circulation of blood inwhich all of these essential characteristics are obtained.

As herein illustrated the improved pump includes two units each havingan inlet and an outlet associated with a pair of reservoirs, preferablyformed of .glass vor other transparent material, and having an openupper end, a closed lower end, and a separate inlet connection. Theinlet and outlet of each pumping unit is connected to a reservoir bymeans of suitable conduit means, and located in each of the conduitmeans extending from a pumping unit outlet is a normally closed valvemeans. Leading from each of the mentioned conduit means, in a locationbetween the pump outlet and the mentioned normally closed valve is aconnection for a conduit means adapted to deliver blood to the patient,while two other conduit means are similarly associated, respectively,with the inlet connections of the reservoirs for receiving blood fromthe patient. .As will presently appear, the four conduit means fordelivering and receiving blood are so cannulated to arteries and veinsof the patient that one .of the pumping units is connected to areservoir for receiving venous blood from the venae cavae and thispumping unit forces the blood into the pulmonary artery and thence tothe lungs, this pumping unit thus functioning to perform the pumpingaction of the right auricle and right ventricle of the patients heart,while the other pumping unit is connected to the other reservoir whichreceives arterial blood from the pulmonary vein, and this pumping unitforces the blood into the aorta and thence through the patients body,this pumping unit thus functioning to perform the pumping action of theleft awhile and left ventricle. Referring again to the two reservoirswhich, as suggested :above, are preferably formed of 'trans parentmaterial, these provide receptacles open to atmospheric pressure forreceiving blood from the patient before this blood enters the pumpingunits. Preferably, and

as herein illustrated, these two reservoirs are connected at their lowerends by a suitable conduit in'which there is a normally closed valvemeans adapted to be opened for by-passing blood from one reservoir'tothe other.

Although there are several well-known types of blood circulating pumpswhich possibly could be used with the apparatus outlined above, thecompressible tube-rotary impeller type which is herein illustratedaffords certain very definite advantages, especially when constructed inthe novel and improved manner about to be explained and in accordancewith features of this invention. In a pump of this type, a compressibletube is supported in a circular shape so as to be progressivelycompressed by the rotary impeller which is usually mounted on an armextending radially from the drive shaft. By arranging'this tube so thatits circular shape is somewhat less than a'full circle, the action ofthe impeller on the tube is interrupted once during each revolution ofthe drive shaft, thus causing the pump to have a cyclic action whichsimulates, at least in a general manner, the pulsations of the *heart.As suggested above, the two pumping units of the novel apparatus of thisinvention take over, respectively, the pumping actions of the right andleft heart. It therefore may be desirable, during use-of the apparatusto circulate the blood of a patient, to change the cyclic rate of thetwo pumping units and/or'to vary the pumping action of one or the otherof the two pumping units. For this purpose, and in accordance withfeatures of this invention, the two pumping units are associated with acommon drive shaft, the speed of which may be varied to change thecyclic rate of the two pumping units, while the rotary impeller of eachpumping unit is mounted on an associated drive'shaft arm for radialadjustment thereon for varying the action of the impeller on thecompressible tube and hence the pumping action of the unit. Moreparticularly, with reference to the radial adjustment of the rotaryimpeller, novel adjusting mechanism "is provided which includes acontrol member readily accessible to, and adapted to .be seized by anoperator, and which is arranged by movement axially of the drive shaftin one direction or the other to effect radial adjustment .of the rotaryimpeller in the desired direction in response to rotation of the driveshaft.

The above and other objects and features of the invention will becomeapparent from the following detailed description of the embodimentthereof which is illustrated in the accompanying drawings, and willbepointed out in the claims.

In the drawings,

FIG. 1 is a diagrammatic view of the novel apparatus of this invention;

FIG. 2 is a plan view of .an improved pump used in the novel apparatusshown in FIG. 1, this view also showing mechanism for driving the pump;

FIG. 3 is a view in end elevation, at an enlarged scale and with partsshown in vertical section substantially on line 'IIIIII of FIG. 5 andlooking in the direction of the arrows, of the left-hand portion of theimprovedpump shown in FIG. 2;

FIG. 4 is a view in side elevation of a part of the pump shown in FIG. 5with certain parts omitted or broken away and others shown in verticalsection; and

FIG. 5 is a view in side elevation of the portion of the pump shown inFIG. 3.

Referring to these drawings, the apparatus which is illustrated in partschematically in FIG. 1 comprises two reservoirs 10 and .12 formed ofglass or other transparent material, and of the shape shown. Each ofthese reservoirs has an open upper end and a closed lower end and thetwo reservoirs are physically connected by means of two cross struts 14,15, the latter of which is preferably formed of a tubular member, whilethe former is asolid rod. The upper end of each reservoir is disposed atan angle to the body portion thereof so that when the reservoirs aresupported with their open upper ends extending substantially vertically,their body portions slope downvwhile the reservoir 12 has an inletconnection 22 and three other connections 24, 25 and 26.

Located adjacent to these two reservoirs is a pump comprising twopumping units. shown schematically in '7 FIG. 1, and indicated generallyby reference characters P-1 and P-2. Each of these pumping unitsincludes a compressible tube T-1 (T-2) and a cooperating rotary impellerR-l (R-2) mounted on a radially extending arm A-1 (A-Z). As isillustrated in FIG. 2 of the drawrngs, the arms A-1 and A-2 are mountedon the opposite ends of a common drive shaft S which is arranged to berotated, through suitable speed reducing gearing G, bv means of theoutput shaft of a variable speed drive D driven by a motor M and havinga control handle H. As will presently be explained, there is associatedwith each of the arms A-1 and A-2 an adjusting mechanism adapted to becontrolled by means of a hand knob K-1 (K-2) for causing radial movementof the rotary impeller to varv the action of the rotary impeller on thecompressible tube. The inlet and outlet of the pumping unit P-l areconnected to the two connections 18 and 20 of the reservoir by conduitmeans comprising tubes 30, 32, and connecting glass tubes 31, 33. whilethe inlet and outlet of the pumping unit P-2 are connected to theconnections 24 and 26 of the reservoir 12 by conduit means comprisinntubes 34, 36 and connecting glass tubes 35 and 37. Associated with thetube 32, which is connected to and leads from the outlet of the tube T1of the pumping unit P-l, is a valve means comprising a clamp device 4!?and a branch connection 42 which is located between the mentioned valvemeans and the outlet of the tube T-1. In a like manner, there isassociated with the tube 35. which is connected to and leads from theoutlet of the tube T-2. a valve means comprising a clamp device 44 and abranch connection 46 which is located between the last-mentioned valvemeans and the outlet from the tube T-2. Extending between theconnections 19 and 25 is a tube 48 which provides a bv-pass conduitmeans in which there is a normally closed valve means comprisin a clampdevice 50. Suitable conduit means 52, 54. 56

'and 58 are associated respectively with the inlet connections 16 and 22and the branch connections 42 and The two pumping units P-1, P-2 of thepump are of identical construction, one being a mirror image of theother, so that a detailed description of one of these units, forexamplethe one which is illustrated on the left in completeunderstanding of the construction and mode of operation of the doubleunit pump arrangement of this invention. Referring to FIG. 3 of thedrawings, this pumping unit comprises a housing 60 shaped to provide acircular recess 62 having adjacent to its open end an annular flange 64.This housing is secured to a portion arms A-1 and A-2 of FIG. 1) whichis grooved as indicated at 72 to receive a sliding block 74, held in thegroove by means of a cover 76. Formed integrally with this block is atrunnion 78 on which a roll (corresponding to the rolls R1 and R-2 ofFIG. 1) which serves as a rotary impeller, is journaled. The trunnion 78projects through a clearance slot 82 formed in the arm 70- as shown inFIG. 3.

Secured to the arm 70 is a member 86 having a bore FIGS. 1 and 2 of thedrawings, will be suflicient for a 88 therein for rotatably receivingthe hub 90 of a bevel gear 92. This gear has a clearance hole 94 throughwhich there passes a hollow lead screw 96 which is threaded into the arm70 and to which the aforementioned bevel gear is drivingly connected bymeans of a set screw 98 and keyway 100 formed in the screw 96. The leadscrew 96 is internally threaded to receive a second lead screw 102, ofthe same hand as the screw 96, which is threaded through a bore 104 inthe block 74 and secured thereto by a locknut 106. The lead of the screw96 is different from that of the screw 102 for a purpose which willpresently appear.

For rotating the bevel gear to effect radial adjqustment of the roll 80,the following arrangement is provided. Secured to the arm 70, coaxiallyof the shaft S, is a stud on which there is rotatably and slidablysupported an adjusting knob 112 (corresponding to the knobs K-1 and K4.of FIGS. 1 and 2) having an enlarged hub portion 114 which is providedwith a circumferential groove 116 (FIG. 3). Formed in the arm 70 is aV-groove guideway 120, see FIG. 4, which is inclined downwardly andoutwardly, as indicated in FIG. 3, in

which' there is slidably mounted a block 122 from which there projects astud portion 124. Journaled on this stud portion is a bevel gear 126,held in place by means of a headed screw 128. Surrounding the hub of thegear 126 is the body portion of a yoke member 130 having a pair of arms132, 132 which are received within the annular groove 116 of the hubportion of the adjusting knob 112. Also rotatably and slidably mountedon the stud 110 is a bevel gear 136 the hub of which is grooved asindicated at 140, 140 and projects into a recess 142 formed in the hubportion 114 of the adjusting knob 112. This gear is normally heldyieldingly in the position shown in FIG. 3, by a spring 146, with itshub engaging a stop ring 148 on the stud 110. A relatively lighterspring 150, seated against an adjusting nut 152 on the stud 110,yieldingly holds the knob 112 and its hub por tion 114 in the positionshown in FIG. 3 with the bottom of the recess 142 in engagement with theend of the hub of the gear 136. The hub portion 114 is drivinglyconnected to the gear 136 by means of pins 154, 154 which are receivedwithin the groove 140, 140.

Extending outwardly from the recess 62 are two grooves 160, 162, FIG. 5,which are disposed at substantially right angles to each other andextend generally tangential ,to the outer wall of the recess 62,indiciated in FIG. 3

by the reference character 164. A portion of the annular flange 64 iscut away, as indicated at 166, 168 in FIG. 5 of the drawings to providea recess for a keeper plate 170,

preferably formed of a plastic or other transparent material, which isheld in place by screws 172, 172, 172.

When this keeper plate is removed, a single loop of a compressible tube180, formed of rubber or suitable jplastic materiaL'may be placed in therecess in engagement with the outer wall 164 thereof and with itsopposite ends extending outwardly through the grooves 160, 162

.which are of a width substantially equal to the normal outside diameterof the tube. The grooves 162 are of the same depth as the recess 62 andinasmuch as the axial distance of the bottom of this recess to theinside of the flange 64, which is just sufiicient to accommodate thetube when it is fully flattened by the roll 80. is somewhat less thantwice the diameter of the tube, the ends of the tube, as they projectoutwardly beyond the housing 60, are deflected slightly away from eachother out .of the central plane of this housing.

during each revolution ofthe shaft S, while the roll 80 travels from aposition"-a on one=end of the loop of the tube to a -pos'ition b on theother-end of the loop. The output of the pump can be varied'in twodifferent ways, e.g., 'by increasing or'decreasing the amount thetube'180 is compressed by the roll 80 and/or by increasing or decreasingthe speed of rotation of the shaft S. As will be apparent, the latteralso has the effect of varying the cyclic rate of the pump, i.e., therate at which the pumping action is interrupted as above explained.

When the parts are in the positions in which they are shown in FIG. 3 ofthe drawings, the gear 136 is out of mesh with the gears 92 and 126,while the gear 126 is partially meshed with the gear 92. Now,:if-theoperator wishes to cause the roll to move radially outwardly along thearm 70, thereby to increase the pumping action, he grasps the knob 112and pulls it outwardly, i.e., to the right FIG. 3, on the stud 110. As aresult of this movement of the knob 112 and its hub portion 114, thegear 126 is moved downwardly completely in mesh with the gear 92 andoutwardly into mesh with the gear 136, which latter gear is being heldagainst axial movement by ring 148 and against rotation by the operatorthrough the action of the pins 154, 154 on the grooves 140, 140.Therefore, as the arm 70 revolves in the direction of the arrow in FIG.5 of the drawings, the gear 126 will be driven in a clockwise directionas viewed in FIG. 3, thus driving the gear 92 and screw 96 in adirection to cause the screw 96 to move upwardly wtihin the arm 70, asviewed in FIG. 3. At the same time, the screw 96 tends to draw the screw102 downwardly, in a manner which will be apparent. Inasmuch as the leadof the screw 96 is greater than the lead of the screw 102, the netresult will be a movement of the block 74 and roll 80 upwardly at a veryslow rate. For example, with a lead on the screw 96 of ,4, and a lead onthe screw 102 of 49. the block 74 will be moved upwardly, i.e., radiallyoutwardly along the arm 70, approximately .0035" for each revolution ofthe gear 97. As soon as the operator releases the knob 112 it isreturned to the position shown in FIG. 3 by the spring 150 and radialmovement of the roll 80 will cease. In order to effect radial movementof the roll in the opposite direction, thereby to reduce the pumpingaction, the operator grasps the knob 112 and pushes it inwardly, i.e.,to the left as viewed in FIG. 3. This causes the gear 136 to be engagedwith the gear 92. Inasmuch as the gear 136 is held against rotation bythe operator, in the manner explained above, as the arm 70 revolves inthe direction of the arrow in FIG. 5, the gear '92 will be driven in adirection to effect radial movement of the roll 80 radially inwardlyalong the arm 70 toward the axis of the shaft S at the rate indicatedabove, i.e., approximately .0035" for each revolution of the gear 92.During this rotation :of gear 92, the gear 126 turns idly. As will beapparent, the adjusting mechanism. which .has been described aboveprovides a very sensitive adjustment of the roll 80 and as a resultaffords an extremely accurate control over the pumping action of theunit. In order to adjust screws 96 and 102, relatively to each other,the nut 106 is removed and the screw 102 is threaded out of the screw 96and the block 74. Now, the screw 96 may be adjusted by manual rotation,after which, with the block 74 held in the desired location and thescrew 96 held against rotation, the screw 102 may be rethreaded into thescrew "96 and block 74 and the nut 106 replaced. As will be apparent,when the roll 80 is being adjusted outwardly, to increase the pumpingaction, the screw 96 travels upwardly toward the block 74. Thus, bysuitable adjustment of the screws 96' and 102, the outward limit ofmovement of the roll can be so determined that complete closure of thetube 180 isprevented and the possible damage to the corpuscles whichmight occur in this way avoided.

6 The mode of operation of the apparatus will now beoutlined'withparticular re'ferenceto FIGS. 1 and 2 of the "drawings. Theapparatus is set up in the operating room adjacent to the patient withthe two reservoirs 10, 12 mounted on a suitable stand, or other type ofsupport, at a level somewhat below the patient and with the pump unit,see FIG. 2, located close by on the floor. In order to save valuablefloor space, the pump unit may be supported on a suitable frame and inthe vertical position shown in FIG. 2. Without attempting to explain thedetails of the surgical procedure involved, which forms no part of .thepresent invention, the conduit means 52, 54, 56 and 58 are cannulatedwith appropriate blood vessels of the patient, as diagrammaticallyillustrated in .FIG. 1, so that the patients heart is entirely bypassed.Initially, each of the .two reservoirs is partially filled with a salinesolution, or with blood, and with the values 40, 44 opened the pump isstarted. Now, as blood fiows from the pulmonary vein into the reservoir10 through the conduit 52 and from venae cavae into the reservoir 12through the conduit 54, these valves are gradually closed to cause thepump units to circulate the oxygenated blood which flows into thereservoir 10 through the body of the patient and the venous blood whichflows into the reservoir 12 to the lungs of the patient.

The speed of rotation of the common drive shaft S of the pump is set, bymeans of the control handle H on the variable speed drive D, Fig. 2, sothat the cyclic action of the two pumping units is comparable to thenormal pulse of the patient, which this cyclic action of the .pumpsimulates, while the pumping action of each pumping unit P-1 and P-2 isinitially adjusted to approximate that required to take care of theblood which flows into the two reservoirs and to equalize the flowthrough the reservoir 10 with thefiow through reservoir 12. This stateof equality of how, or the lack thereof, is readily apparent to theoperator by his observation of the level of the blood within these tworeservoirs, which, as already indicated, are made of transparentmaterial for this purpose. As will be apparent, the flow of bloodthrough the reservoir '10 may be very quickly and accurately regulatedby the operator through a suitable manipulation of the control knob K-l,while the flow through the reservoir 12 can similarly be regulated bymeans of the knob K-2. In this manner the action of the pump can .becontrolled in accordance with the requirements of the patient during theoperation. In the .event thatsuch action should become necessary for anyreason, the quantity of the blood in the two reservoirs may be veryquickly balanced by temporarily opening the by-pass valve 50.1ocated inthe conduit 48. The hollow strut 15 provides an automatic by-pass forpreventing overflow of one or the other ofthe reservoirs 10 or 12 shouldthe level of the blood therein rise to an unduly high level.

The cyclic rate of the pump, i.e., the simulated pulse, may be readilyincreased or decreased by varying the speed of rotation of the commondrive shaft S in the manner explained above and this change will be thesame for each of the two units which, as explained above, correspond tothe right and left sides of the heart. After such a change in the cyclicrate of the pump it may be necessary for the operator to make a slightreadjustment in the pumpingaction of the two units in order to maintainthe desired quantity and equality of flow through the two reservoirs.This can, of course, be readily accomplished in the manner explainedabove.

As will be apparent, with the apparatus of this invention, a singleoperator is enabled to control the operation of the pump and to regulatethe flow through the two reservoirs in any desired manner appropriate toconditions met during the operation. Moreover, the novel and improvedpump is very dependable in action and, because of the simplicity of itsconstruction,there is little, if'any, likelihood of mechanicaldifliculties arising. The pump 7 tube 180 (T-l or T-2) is very easilyreplaceable in the event of damage during use and, should mechanicalfailure of one or both of the pumping units occur during an operation,these tubes could be quickly removed and placed in another standby pumpwith only a very brief interruption of the circulation of blood. Asexplained above, the limit of outward adjustment of the pressure roll 80may be such that the compressible tube used in each pumping unit cannever be entirely closed by the roll. Thus danger of damage to the bloodby squeezing of the corpuscles may be effectively avoided. In addition,the action of the rotary impeller in moving the blood through thecompressible tube is an easy one and such that other damage to the bloodis avoided.

After use, the various pieces of tubing which have been employed for theseveral conduits referred to above, as well as the two pieces of tubingused in the pumping units themselves, may be entirely discarded or, ifdesired, these pieces of tubing may be cleaned and sterilized for futureuse. The same is also true with respect to the two reservoirs which maybe made of glass or of a suitable transparent plastic of a type whichcan be either sterilized or such as would warrant being discarded afteruse.

The two reservoirs are connected together by the struts to form oneunit. As indicated above, this unit is mounted on a suitable stand at alevel slightly below that of the patient. As the blood flows into thesetwo reservoirs through the conduit means provided, a syphon eifect isproduced. This syphon effect may be increased or decreased by loweringor raising the two reservoirs, which is easily accomplished because oftheir simple construction, to facilitate or retard the rate of flow ofblood from the patient into the reservoirs. As shown in FIG 1, the inlet22 to the reservoir 12 which receives blood from the venae cavae is solocated that the blood flows some distance down along the inner wall ofthe inclined body portion of the reservoir. This, it has been found,tends to avoid foaming of the blood and also provides a convenientvisual indication of the rate of fiow of blood from the patient. On theother hand, the inlet 16 to the reservoir 12, which receives blood fromthe pulmonary vein, is located well below the level of blood in thatreservoir to avoil entrainment of air. By providing the connections 18,20 and 24, 26 adjacent to the lower portion of their respectivereservoirs, the operator can, by maintaining the level of blood in thesereservoirs well above these connections, avoid any danger of airentering the circulating blood stream. Should occasion require, bloodfrom a donor may be added to either one or both of the reservoirsthrough their open upper ends and an automatic gravity feed device maybe provided for this purpose.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

l. A pump for use in the extracorporeal circulation of blood comprisinga pair of pumping units each having a circular shaped compressibletubular pumping member, a support for each of said pumping members, apump shaft extending through said supports and centrally locatedrelatively to said circular pumping members, a pair of arms secured tosaid shaft, an impeller member mounted for radial adjustment on each ofsaid arms and adapted to cooperate with one of the pumping members, anda separate means carried by each of said arms for radially adjusting theimpeller member mounted thereon to vary the action of said impellermember on its associated pumping member during the operation of thepumping unit, and power-operated means for rotating said pump shaft.

2. A pump for use in the extracorporeal circulation of blood comprisinga pair of pumping units each having a circular shaped compressibletubular pumping member,

a support for each of said pumping members, a pump shaft extendingthrough said supports and centrally located relatively to said circularpumping members, a

pair of arms secured to said shaft, an impeller member mounted forradial adjustment on'each of said arms and adapted to cooperate with oneof the pumping members, a separate means carried by each of said armsand manually operable to effect radial adjustment of the impeller memberthereon to vary the action of said impeller member on its associatedpumping member during the operation of the pumping unit, andpower-operated means for rotating said pump shaft.

3. A pump for use in the extracorporeal circulation of blood comprisinga pair of pumping units each having a circular shaped compressibletubular pumping member, a support for each of said pumping members, apump shaft extending through said supports and centrally locatedrelatively to said circular pumping members, a pair of arms secured tosaid shaft, a rotary impeller member mounted for radial adjustment oneach of said arms and adapted to cooperate with one of the pumpingmembers, means carried by each of said arms and shiftable in directionsextending axially of the pump shaft to effect radial adjustment of theimpeller member thereon in response to rotation of the pump shaft tovary the action of said impeller member on its associated pumping memberduring operation of the pumping unit, and poweroperated means forrotating said pump shaft.

4. A pump having a circular shaped compressible tubular pumping member,a support for the pumping member, a pump shaft extending through saidsupport and centrally located relatively to the circular pumping member,an arm secured to said pump shaft, a rotary impeller mounted on said armfor radial adjustment and adapted to cooperate with the pumping member,means carried by the arm and shiftable in directions extending axiallyof said pump shaft to effect radial adjustment of said rotary impellerthereon in response to rotation of said pump shaft to vary the action ofthe impeller on the pumping member during the operation of the pump, andpower-operated means for rotating the pump shaft.

5. A pump for use in the extracorporeal circulation of blood comprisinga pair of pumping units each having a circular shaped compressibletubular pumping member, a support for each of said pumping members, apump shaft extending through said supports and centrally locatedrelatively to said circular pumping members, a pair of arms secured tosaid shaft, a rotary impeller member mounted for radial adjustment oneach of said arms and adapted to cooperate with one of the pumpingmembers, an adjusting knob carried by each of said arms and shiftableaxially of said pump shaft, means controlled by said knob and operableto effect radial adjustment of the impeller member thereon in responseto rotation of the pump shaft to vary the action of said impeller memberon its associated pumping member during the operation of the pumpingunit, and power-operated means for rotating said pump shaft.

6. A pump having a circular shaped compressible tubular pumping member,a support for the pumping member, a pump shaft extending through thesupport-and centrally located relatively to said circular pumpingmemher, an arm secured to said pump shaft, a rotary impeller mounted onsaid arm for radial adjustment and adapted to cooperate with the pumpingmember, an adjusting knob carried by said arm and shiftable indirections extending axially of said pump shaft, means controlled bysaid knob and operable to effect radial adjustment of the impellerthereon in response to rotation of the pump shaft to vary the action ofsaid impeller on the pumping member during the operation of the pump,and power-operated means for rotating the pump shaft.

7. A pump for use in the extracorporeal circulation of blood comprisinga pair of pumping units each having a circular shaped compressiblepumping member, a support for each of said pumping members, a pump shaftextending through said supports and centrally located relatively to saidcircular pumping members, a pair of arms secured to said shaft, a rotaryimpeller mounted on each of said arms for radial adjustment and adaptedto cooperate with one of the pumping members, a differential screwassociated with each arm for eifecting radial adjustment of the impellermounted thereon, a reversible drive mechanism carried by each arm foroperating the screw associated therewith, an adjusting knob carried byeach of said arms and shiftable in directions extending axially of saidpump shaft for controlling the drive mechanism carried thereby to causerotation of its screw in response to rotation of the pump shaft toeifect radial adjustment of the impeller on said arm thereby to vary theaction of the impeller on its associated pumping member, andpower-operated means for rotating the pump shaft.

8. A pump having a circular shaped compressible tubular pumping member,a support for the pumping member, a pump shaft extending through thesupport and centrally located relatively to said circular pumpingmember, a rotary impeller mounted on said arm for radial adjustment andadapted to cooperate with said pumping member, a differential screw foreffecting radial adjustment of the rotary impeller, a reversible drivemechanism for operating said screw, an adjusting knob carried by saidarm and shiftable in directions extending axially of said pump shaft forcontrolling the drive mechanism to cause rotation of the screw inresponse to rotation of the pump shaft to efiect radial adjustment ofsaid impeller on said arm thereby to vary the action of the impeller onthe pumping member, and power-operated means for rotating the pumpshaft.

References Cited in the file of this patent UNITED STATES PATENTS459,053 Traux Sept. 8, 1891 459,055 Traux Sept. 8, 1891 487,136 TrauxNov. 29, 1892 1,099,473 Sundh June 9, 1914 1,284,212 Barber Nov. 12,1918 1,703,361 Pohl Feb. 26, 1929 2,319,485 Alabrune May 18, 19432,334,148 Jones Nov. 9, 1943 2,612,839 Denny Oct. 7, 1952 2,651,264Bmckmann Sept. 8, 1953 2,652,831 Chesler Sept. 22, 1953 2,705,493Malmros et al. Apr. 5, 1955 2,787,456 Bowman Apr. 2, 1957 2,789,514 HillApr. 23, 1957 2,807,213 Rosen Sept. 24, 1957 FOREIGN PATENTS 21,859Great Britain of 1892 339,735 'France June 17, 1904

